The main ingredient in the French dessert financier is almond. Traditional financiers are small cakes made with ground almonds or almond flour, egg whites, powdered sugar, flour, and browned butter.
The cake originated in France and was formerly known as a visitandine. It was popularized in the 19th century, when Parisian bakers gave it a small rectangular shape resembling a gold bar—an appearance associated with financiers and the Paris financial district.
Browned butter, called beurre noisette, gives the cake its characteristic nutty aroma and helps create a moist center with a lightly crisp exterior. The almond flavor is central, even though some modern versions add pistachios, hazelnuts, fruit, or chocolate.
A common mix-up is confusing a financier with a madeleine. Both are small French cakes, but madeleines are typically sponge-like and shell-shaped, while financiers are denser, almond-based, and traditionally rectangular.